This invention relates to a novel means of packaging solid or gelled heating fuels.
Solid or gelled heating fuels have wide potential application as convenient, easily handled and comparatively safe heat sources. Gelled heating fuels in portable form can be employed in civilian uses such as camping, outdoor cooking of all sorts, fire-starting, emergency heat and light supplies, and the like. Gelled heating fuels are also essential for military use, including the heating of field rations, etc.
The most widely accepted forms of gelled heating fuels at present are ethyl alcohol gelled with a metallic soap and trioxane formed from compaction of powdered trioxane with or without compaction aids such as magnesium stearate and an organic binder, or a trioxane melt. Compacted or melted, and then molded or otherwise shaped, gelled heating fuel such as trioxane in the shape of pellets is advantageous in view of the lack of toxicity and ease of ignition of this fuel. The low luminosity of trioxane fuel is especially useful for military applications. However, gelled heating fuels have not proven to be fully satisfactory. Trioxane fuel pellets and the like have a rather low caloric value on the order of 4,000 kcal/kg. Moreover, although the low luminosity of trioxane and other oxygenated hydrocarbon gelled fuels may be advantageous in military field applications, the rather non-luminous flame is not easily detected and may lead to accidental burns and fires.
In accordance with the invention described in copending, commonly assigned U.S. patent application Ser. No. 836,792, filed Mar. 6, 1986, it is possible to increase the luminosity of the flame obtained from solid trioxane fuel by adding thereto certain non-toxic sodium salts. Additionally, copending, commonly assigned U.S. patent application Ser. No. 836,889, filed Mar. 6, 1986, describes increasing the caloric content of trioxane fuels by adding thereto dialkyl ethers of alkanediols. By such improvements to trioxane heating fuels it is believed that these fuels will be more readily accepted as a convenient and safe portable energy source.
While the heat content of gelled fuels can be increased and the luminosity of the flame increased for improved safety such as just described for trioxane fuel, many gelled fuels are still particularly disadvantageous because such fuels readily evaporate, i.e, sublime, from the containers under normal atmospheric conditions. Accordingly, gelled fuels which are highly volatile must be kept in tightly sealed containers to prevent excessive loss by sublimation. A typical container or package for a solid or gelled fuel pellet comprises a metal film, such as aluminum foil wrapped tightly around the fuel pellet. Thus, to use the fuel, the metal foil must be unwrapped and the unwrapped fuel subsequently ignited. Unwrapping the tightly wrapped package prior to using the gelled heating fuel is an inconvenience. This lack of convenience is more readily apparent in military field applications where time, safety, and ease of comfort are important considerations.
A known method of packaging solid or gelled fuels, in particular, starter or decorative logs for fireplace use, comprises wrapping the log-shaped fuel in a combustible paper wrapper. To use such fuels, the paper wrapper is ignited, such as along an edge of the wrapper, and the solid log-shaped fuel is subsequently ignited by the flame from the packaging. The paper packaging is not removed prior to use. As discussed above, many gelled fuels and, in particular, gelled oxygenated hydrocarbon fuels evaporate from the containers even under normal atmospheric conditions. Accordingly, a paper covering or package for highly volatile fuels would be wholly unsatisfactory because such porous coverings would not prevent sublimation of the fuel. Moreover, it is unlikely that a paper package could be tightly wrapped around a gelled fuel pellet and the like to hermetically seal the fuel pellet to prevent sublimation.
It would be an obvious advantage if readily sublimable solid or gelled fuels could be hermetically packaged in a flammable wrapper. Accordingly, it is an object of the present invention to provide a combustible wrapper for solid or gelled fuels to eliminate the need for unwrapping the package to ignite the solid fuel. Another object is to package highly volatile solid or gelled fuels in a combustible wrapper which is capable of hermetically sealing the fuel to prevent sublimation.
These and other objects, aspects, and advantages of the invention will be readily apparent to those of ordinary skill in the art on consideration of the following description of the invention.